1. Field of the Invention
The present invention relates to a drawing apparatus that performs drawing on a substrate with a plurality of charged particle beams.
2. Description of the Related Art
In recent years, as micronization of the element, increasingly complex circuit patterns, or a higher capacity of pattern data advance, the drawing accuracy as well as drawing throughput of drawing apparatuses for use in the manufacturing of devices such as semiconductor integrated circuits needs to be improved. As a method for realizing that ideal, a multiple beam-type electron beam drawing apparatus is known in which a plurality of electron beams (charged particle beams) is deflected or the ON/OFF operation of the irradiation of electron beams is independently controlled so as to draw predetermined drawing data at the predetermined position of a substrate to be treated. Japanese Patent Laid-Open No. 9-7538 discloses a charged particle beam drawing apparatus that independently controls the ON/OFF operation of a plurality of electron beams using a blanking deflector (blanking deflector array).
Here, in the blanking deflector, a pair of electrodes are arranged so as to be facing an electron beam passing through each electron beam opening, where each of the electrodes is connected to a wire. At this time, voltage is applied between the electrodes and an electron beam is electrostatically deflected so as to be directed onto a stopping aperture, whereby the electron beam is turned OFF (subject to blanking). In other words, when a defect in an electrode or a disconnection of a wire occurs, voltage cannot be applied between the electrodes, and thus, an electron beam cannot be turned OFF. An opening where the irradiation of the electron beam is incapable of being turned OFF is referred to as a “white defect” of a blanking deflector. In contrast, an opening where the irradiation of the electron beam is incapable of being turned ON in a complete way due to the adhesion of dust on the opening is referred to as a “black defect”. Furthermore, an opening where the irradiation of the electron beam is capable of being turned ON only in an incomplete way is referred to as a “gray defect”. It should be noted that a black defect and a gray defect may occur not only due to the blanking deflector but also due to the adhesion of dust on the openings of, for example, an aperture array, an electrostatic lens, a blanking aperture, other deflector, or the like or a disconnection of a wire. The occurrence probability of such a defect in the blanking deflector tends to increase due to the micronization of electron beam or opening or the increase in the number of electron beams in association with the improvement in micronization of semiconductor integrated circuits or the improvement in productivity. Since the presence of such a defect prevents the electron beam drawing apparatus from drawing a pattern accurately, the position of a defect and the type thereof (white defect, black defect (gray defect)) need to be detected accurately at high speed.
Accordingly, Japanese Patent No. 4058059 discloses an electron beam current measuring method for detecting an anomaly of an electron beam in a multiple beam-type electron beam drawing apparatus. In the anomaly detection method, an electron beam(s) other than the specified position is firstly subject to blanking, and only the specified electron beam is irradiated to an electron beam detector. Next, electron beam current measurement is executed using a measurement parameter set to a value corresponding to measurement accuracy so as to judge whether an electron beam is normal or defective by comparing the measured value with a predetermined value.
Here, assume the case in which a defect (white defect, black defect, or gray defect) in a blanking deflector is detected using the anomaly detection method disclosed in Japanese Patent No. 4058059. Firstly, only an electron beam, of which the exposure dose is intended to be measured, is turned ON to be irradiated to an exposure dose measuring sensor for a predetermined time. At this time, when the measured exposure dose is as close to zero as possible, it is determined that a black defect occurs. In contrast, when the measured exposure dose does not reach a predetermined value, it is determined that a gray defect occurs, whereas, when the measured exposure reaches a predetermined value, it is determined that the blanking deflector is in a normal state or a white defect occurs. In this case, the electron beam is turned OFF and then irradiated to an exposure dose measuring sensor for a predetermined time. When the exposure dose at that time is equal to or greater than a predetermined value, it is determined that a white defect occurs, whereas, when the exposure dose is zero, it is determined that the blanking deflector is in a normal state. In general, in a multiple beam-type electron beam drawing apparatus, the number of electron beams is in the range of from several tens of thousands to several hundreds of thousands. Therefore, the implementation of the anomaly detection method described above to all electron beams needs a very large amount of time.